Insulin sensitivity didn't improve in obese women even after losing weight when they followed high-protein diets, report researchers from the Washington University School of Medicine in St. Louis.
It's common for people looking to lose weight to try and stave off hunger and muscle loss by turning to protein-rich foods. However, in a study published in the journal Cell Reports, the researchers showed that consuming too much protein hampers insulin sensitivity, which is crucial in reducing diabetes risk.
Bettina Mittendorfer, Ph.D. and colleagues worked with 34 obese women between the ages of 50 and 65. All of the subjects had body mass indexes of 30 or more but none had been diagnosed with diabetes. The women were also randomly assigned to one of three groups.
For 28 weeks, the control group was tasked with maintaining their weight, while one group was given a weight loss diet plan that integrated the recommended daily protein allowance of 0.8 grams for every kilogram of body weight. Those belonging to the third group were assigned high-protein diets where they ate 1.2 kilograms of protein for every kilogram of body weight.
For someone who is 55 years old and weighs 180 pounds, following the recommended daily allowance would mean a protein allocation of 65 grams per day. For those given excess protein, a woman of the same age and weight would be eating 100 grams of protein a day.
All meals were provided by the researchers to ensure proper protein content. They wanted to zero in on the relationship between protein and weight loss, so the researchers only tweaked protein content in the meals, carrying out minimal changes to fat or carbohydrate content.
According to Mittendorfer, lost weight is typically two-thirds fat tissue and one-third lean tissue. Women who consumed more protein did have a tendency to lose less lean tissue but total difference came up to only about a pound.
"We question whether there's a significant clinical benefit to such a small difference," said Mittendorfer.
Given that, the researchers are more interested in promoting the consumption of protein as recommended. Not to mention that they saw that women eating their recommended daily protein allowance enjoyed big metabolism benefits, logging in 25 to 30 percent improvements in insulin sensitivity.
It's not clear why exactly improvements in insulin sensitivity were negated in those who ate high-protein diets, so Mittendorfer is planning on carrying out further research on the topic. Additionally, she wants to know if the same results will be observed in men.
The study received funding support from the Longer Life Foundation, the Central Society for Clinical and Translational Research Early Career Development Award, the National Institute of General Medical Sciences and the National Institute of Diabetes and Digestive and Kidney Diseases.
